This invention relates to a small motion transducer positioner for use in a micropositioning device to control the position of a probe tip relative to the surface of a sample under observation and, more particularly, to an improved positioner for eliminating Abba offset error even though tilting of the positioner is effected.
Segmented piezoceramic tubes are commonly used as actuators to produce probe tip motion in micropositioning devices such as scanning probe microscopes and profilometers. Such actuators have the advantages of simplicity, long range, small size and stiffness. What is disadvantageous about these actuators is the unpredictable tilting of the end of the tube, which introduces motion that is difficult to measure. This problem, known in the field of dimensional metrology as Abba offset error, is described, for example, in the article "Dimensional Metrology with Scanning Probe Microscopes" J. Appl. Phys., Volume 74, No. 9, Nov. 1, 1993, pages 83-109. U.S. Pat. No. 5,306,919, issued Apr. 26, 1994, to Elings et al proposes a solution to the problem of unwanted tilting by bending a piezoelectric tube into an S shape. This proposed solution is not entirely satisfactory because the bending leads to unpredictable tilting. It is therefore a primary object of the present invention to provide a positioner for a micropositioning device which eliminates unpredictable tilting so that Abba offset error is eliminated.
It would also be desirable to provide such a positioner which magnifies actuator movement to achieve long range, is thermally compensated, can be used for two and three dimensional motion, and is of simple construction. It is therefore another object of the present invention to provide a positioner possessing all of these attributes.